What is Free Evolution?
Free evolution is the concept that natural processes can cause organisms to develop over time. This includes the appearance and development of new species.
Many examples have been given of this, including various kinds of stickleback fish that can be found in salt or fresh water, as well as walking stick insect varieties that favor particular host plants. These typically reversible traits cannot explain fundamental changes to basic body plans.
Evolution by Natural Selection
The evolution of the myriad living organisms on Earth is an enigma that has intrigued scientists for centuries. Charles Darwin's natural selection is the best-established explanation. This happens when people who are more well-adapted have more success in reproduction and survival than those who are less well-adapted. Over time, the population of individuals who are well-adapted grows and eventually develops into a new species.
Natural selection is an ongoing process and involves the interaction of 3 factors including reproduction, variation and inheritance. Sexual reproduction and mutations increase the genetic diversity of a species. Inheritance refers to the transmission of a person's genetic traits, including recessive and dominant genes and their offspring. Reproduction is the process of generating fertile, viable offspring. This can be accomplished through sexual or asexual methods.
Natural selection is only possible when all the factors are in equilibrium. For instance the case where the dominant allele of the gene causes an organism to survive and reproduce more often than the recessive one, the dominant allele will become more prominent in the population. If the allele confers a negative advantage to survival or reduces the fertility of the population, it will be eliminated. The process is self-reinforcing, which means that an organism with an adaptive trait will live and reproduce much more than those with a maladaptive trait. The more fit an organism is as measured by its capacity to reproduce and survive, is the more offspring it can produce. People with desirable traits, such as having a longer neck in giraffes, or bright white patterns of color in male peacocks, are more likely to survive and produce offspring, so they will make up the majority of the population over time.
Natural selection is only an aspect of populations and not on individuals. This is a crucial distinction from the Lamarckian theory of evolution that states that animals acquire traits either through use or lack of use. For instance, if the giraffe's neck gets longer through reaching out to catch prey, its offspring will inherit a larger neck. The length difference between generations will continue until the neck of the giraffe becomes so long that it can not breed with other giraffes.
Evolution through Genetic Drift
In genetic drift, alleles of a gene could be at different frequencies within a population through random events. In the end, one will attain fixation (become so widespread that it can no longer be removed by natural selection), while other alleles fall to lower frequency. In the extreme it can lead to one allele dominance. The other alleles are eliminated, and heterozygosity is reduced to zero. In a small group, this could result in the complete elimination of recessive gene. This is called a bottleneck effect, and it is typical of the kind of evolutionary process that occurs when a large number of individuals migrate to form a new group.
A phenotypic bottleneck may occur when survivors of a disaster such as an epidemic or mass hunting event, are condensed within a narrow area. The survivors will share an allele that is dominant and will have the same phenotype. This could be caused by war, earthquake, or even a plague. Regardless of the cause, the genetically distinct population that remains is prone to genetic drift.
에볼루션코리아 , Lewens, and Ariew use a "purely outcome-oriented" definition of drift as any departure from the expected values of variations in fitness. They give a famous instance of twins who are genetically identical, share identical phenotypes, but one is struck by lightening and dies while the other lives and reproduces.
This type of drift is vital to the evolution of the species. It's not the only method of evolution. The most common alternative is to use a process known as natural selection, in which the phenotypic diversity of the population is maintained through mutation and migration.
Stephens argues there is a vast difference between treating drift like an actual cause or force, and considering other causes, such as migration and selection as causes and forces. He argues that a causal mechanism account of drift allows us to distinguish it from the other forces, and that this distinction is vital. He further argues that drift is both a direction, i.e., it tends to eliminate heterozygosity. It also has a size, which is determined based on population size.
Evolution by Lamarckism
When students in high school study biology, they are often introduced to the work of Jean-Baptiste Lamarck (1744 - 1829). His theory of evolution is commonly known as "Lamarckism" and it asserts that simple organisms evolve into more complex organisms through the inherited characteristics that result from the organism's natural actions usage, use and disuse. Lamarckism is illustrated through an giraffe's neck stretching to reach higher branches in the trees. This would cause the longer necks of giraffes to be passed onto their offspring who would then grow even taller.
Lamarck was a French Zoologist. In his inaugural lecture for his course on invertebrate Zoology at the Museum of Natural History in Paris on the 17th May 1802, he presented a groundbreaking concept that radically challenged the previous understanding of organic transformation. In his view living things evolved from inanimate matter through the gradual progression of events. Lamarck wasn't the first to propose this however he was widely regarded as the first to give the subject a comprehensive and general explanation.
The prevailing story is that Lamarckism became a rival to Charles Darwin's theory of evolution by natural selection, and both theories battled it out in the 19th century. Darwinism eventually triumphed and led to the creation of what biologists now call the Modern Synthesis. This theory denies the possibility that acquired traits can be acquired through inheritance and instead argues that organisms evolve through the selective action of environmental factors, including natural selection.
Lamarck and his contemporaries endorsed the notion that acquired characters could be passed on to future generations. However, this concept was never a central part of any of their evolutionary theories. This is due in part to the fact that it was never tested scientifically.
It's been more than 200 years since Lamarck was born and, in the age of genomics there is a huge amount of evidence that supports the possibility of inheritance of acquired traits. This is sometimes referred to as "neo-Lamarckism" or, more commonly epigenetic inheritance. It is a form of evolution that is just as valid as the more popular Neo-Darwinian theory.
Evolution through Adaptation
One of the most popular misconceptions about evolution is its being driven by a struggle to survive. In fact, this view is inaccurate and overlooks the other forces that determine the rate of evolution. The struggle for survival is more accurately described as a struggle to survive within a particular environment, which may include not just other organisms, but as well the physical environment.
Understanding adaptation is important to understand evolution. It refers to a specific characteristic that allows an organism to survive and reproduce in its environment. It can be a physiological structure, such as fur or feathers or a behavioral characteristic like moving into shade in hot weather or stepping out at night to avoid the cold.
An organism's survival depends on its ability to draw energy from the environment and to interact with other living organisms and their physical surroundings. The organism must possess the right genes to produce offspring, and must be able to find sufficient food and other resources. The organism should also be able to reproduce at a rate that is optimal for its specific niche.
These factors, along with gene flow and mutation, lead to a change in the proportion of alleles (different varieties of a particular gene) in the gene pool of a population. As time passes, this shift in allele frequency can result in the emergence of new traits and ultimately new species.
Many of the characteristics we admire in animals and plants are adaptations. For instance the lungs or gills which extract oxygen from the air feathers and fur as insulation and long legs to get away from predators, and camouflage to hide. To comprehend adaptation it is essential to differentiate between physiological and behavioral traits.
Physiological adaptations like thick fur or gills, are physical characteristics, whereas behavioral adaptations, such as the tendency to search for companions or to retreat into the shade in hot weather, are not. It is also important to remember that a insufficient planning does not cause an adaptation. A failure to consider the implications of a choice even if it seems to be logical, can cause it to be unadaptive.